Liquid crystal display

ABSTRACT

A liquid crystal display includes a first insulating substrate. A pixel electrode is formed on a top surface of the first insulating substrate. The pixel electrode has a first opening pattern at each pixel area. The pixel electrode is substantially rectangular in shape with first and second long sides, and first and second short sides. The pixel electrode is divided into an upper region defined by the first and second long sides and first short side, and a lower region defined by the first and second long sides and second short side. A common electrode is formed on a bottom surface of a second insulating substrate, and has a second opening pattern at each pixel area. The first and second opening patterns each have a plurality of openings, the openings of the first opening pattern and the second opening pattern being alternately arranged parallel to each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.13/466,643 filed on May 8, 2012 which is a continuation of U.S. patentapplication Ser. No. 12/502,854 filed on Jul. 14, 2009, now U.S. Pat.No. 8,174,651 issued May 8, 2012, which is a Continuation of U.S. patentapplication Ser. No. 11/557,670 filed on Nov. 8, 2006, now U.S. Pat. No.7,583,345 issued on Sep. 1, 2009, which is a divisional of U.S. patentapplication Ser. No. 11/175,322, filed on Jul. 7, 2005, now U.S. Pat.No. 7,154,577 issued on Dec. 26, 2006, which is a continuation of U.S.patent application Ser. No. 10/838,346, filed on May 5, 2004, now U.S.Pat. No. 6,952,247 issued on Oct. 4, 2005, which is a continuation ofU.S. patent application Ser. No. 09/676,812, filed on Oct. 2, 2000, nowU.S. Pat. No. 6,738,120 issued on May 18, 2004, which claims priority toKorean Patent Application No. 1999-42216, filed on Oct. 1, 1999, thedisclosures of which are all incorporated by reference herein in theirentirety.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display (LCD) and,more particularly, to an LCD in which a predetermined opening pattern isformed at pixel and common electrodes such that a wide viewing angle isobtained.

(b) Description of the Related Art

Generally, an LCD has a structure having a liquid crystal layer that issandwiched between two substrates. An electric field is applied to theliquid crystal layer to control the alignment of the liquid crystalmolecules, ultimately controlling the transmittance of incident light.In a vertically aligned (VA) LCD, the liquid crystal molecules arealigned perpendicular to the substrates when an electric field is notapplied. In case two polarizer films are arranged with their polarizingdirections perpendicular to each other, the linearly polarized lightpassing through the first polarizer film is completely blocked by thesecond polarizer film in the absence of an electric field. The completeblockage of lights exhibits a very low brightness in and “off” state ofthe normally black mode. This helps a VA LCD obtain relatively highercontrast ratio than that of the conventional TN liquid crystal display.

However, the liquid crystal molecules are irregularly inclined againstthe substrate when an electric filed is applied. Therefore, in one ormore areas, the long axis directions of some of the liquid crystalmolecules are aligned with the polarizing direction of the firstpolarizer film or the second polarizer film. In such areas, the liquidcrystal molecules cannot rotate the polarizing direction, i.e.,polarization, and the light is completely blocked by the polarizer film.Such areas appear as black portions on the screen, which degrade the inpicture quality. These areas are referred to as areas of “texture.”

In order to solve the above problem, several techniques ofelectrode-patterning have been suggested. However, a slow response timestill remains as a problem.

FIG. 1 illustrates a schematic view of opening patterns formed at pixeland common electrodes in a prior art liquid crystal display. As shown inFIG. 1, the pixel and common electrodes are formed with opening patterns1 and 2, respectively. Each of the opening patterns 1 and 2 is formed ina V-shape and is arranged with ends of the V-shapes in proximity to eachother so that roughly a diamond shape is formed by the opening patterns1 and 2. Liquid crystal material is injected between the pixel electrodeand the common electrode, and liquid crystal molecules 3 are alignedperpendicular to the electrodes.

When an electric field is applied to the liquid crystal material, theliquid crystal molecules 3 come to be arranged parallel to theelectrodes. However, the response speed of the liquid crystal molecules3 with respect to the applied electric field is very slow with theformation of the opening patterns 1 and 2 at the pixel and commonelectrodes. That is, as a result of a fringe field formed due to theopening patterns 1 and 2, the liquid crystal molecules 3 are firstarranged perpendicular to the opening patterns 1 and 2 (A state), thenare aligned to be parallel with one another (B state), because liquidcrystal molecules tend to align themselves roughly parallel along theirlong axes. These two steps of alignment slow down the response speed.

The slow response speed of liquid crystal molecules generatesafter-images when displaying moving pictures on the screen. There istherefore a need to increase the response speed of liquid crystalmolecules.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a liquid crystaldisplay which has an improved response speed and a wide viewing angle.

It is another object of the present invention to provide a liquidcrystal display that shows improved picture images.

These and other objects may be achieved by a liquid crystal displayhaving a first insulating substrate with top and bottom surfaces. Apixel electrode is formed on the top surface of the first insulatingsubstrate. The pixel electrode has a first opening pattern at each pixelarea. The pixel electrode with the first opening pattern issubstantially rectangular in shape and having first and second longsides, and first and second short sides. The pixel electrode is dividedinto an upper region defined by the first and second long sides and thefirst short side, and a lower region defined by the first and secondlong sides and the second short side. A second insulating substrate withtop and bottom surfaces is arranged parallel to the first insulatingsubstrate at a predetermined distance from the same such that the bottomsurface of the second insulating substrate faces the top surface of thefirst insulating substrate. A common electrode is fondled on the bottomsurface of the second insulating substrate. The common electrode has asecond opening pattern at each pixel area, which corresponds to eachpixel area of the pixel electrode. A liquid crystal layer is sandwichedbetween the first and second substrates while contacting the pixel andcommon electrodes.

The first and second opening patterns each have a plurality of openings,the openings of the first and second opening patterns being alternatelyarranged parallel to each other.

The first and second opening patterns each have a middle linear portion.The linear portions of the first and second opening patterns arealternately arranged parallel to each other. The first opening patternincludes a first opening formed in the upper region of the pixelelectrode in a first direction. A second opening portion is formed inthe lower region of the pixel electrode in a second direction normal tothe first direction. The second opening pattern includes a first trunkopening formed in the upper region of the common electrode in the firstdirection, and a second trunk opening formed in the lower region of thecommon electrode in the second direction. The first direction is slantedat a predetermined angle with respect to the long or short sides of thepixel electrode. The second opening pattern further includes firstbranch openings overlapping the first and second short sides of thepixel electrode, and second branch openings overlapping the first andsecond long sides of the pixel electrode. The first opening patternfurther includes a third opening formed where the upper and lowerregions of the pixel electrode meet while proceeding parallel to thefirst and second short sides of the pixel electrode. The second branchopenings each have a width greater than that of the trunk openingportion. The first direction is parallel to one of the long and shortsides of the pixel electrode. The first and second trunk openings eachhave opposite ends respectively with a gradually enlarged width. Out ofthe second trunk openings overlaps the second short side of the pixelelectrode. The first opening has opposite ends respectively with agradually reduced width.

The pixel and common electrodes are overlapped with each other such thatthe first and second opening patterns partition the pixel electrode intoseveral micro-regions. The micro-regions of the pixel electrode are inthe shape of polygons where the longest sides are parallel to eachother. The micro-regions of the pixel electrode are classified into afirst type where the longest sides are arranged in a first direction,and a second type where the longest sides are arranged in a seconddirection normal to the first direction. The first direction is slantedat a predetermined angle with respect to the long or short sides of thepixel electrode. Alternatively, the first direction may be parallel toone of the long and short sides of the pixel electrode.

The first and second opening patterns form fringe fields when voltage isapplied between the pixel and common electrodes. The orienting directionof the liquid crystal molecules due to the fringe fields corresponds tothat of the liquid crystal molecules as a result of a force exerted bythe molecules. It is preferable that the liquid crystal molecules areoriented in four directions. The opening width of the first and secondopening patterns is preferably in the range of 10-16 μm.

The pixel electrode may have protrusions at the sides adjacent to theends of the first and second openings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by referring to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or the similar components, wherein:

FIG. 1 is a schematic view of opening pattern units formed at common andpixel electrodes in a prior art liquid crystal display;

FIG. 2 is a schematic cross sectional view of a liquid crystal displayaccording to a preferred embodiment of the present invention;

FIG. 3A is a schematic view of opening pattern units formed at commonand pixel electrodes according to one example of the present invention;

FIG. 3B is a schematic view of opening pattern units formed at commonand pixel electrodes according to another example of the presentinvention;

FIG. 4A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 4B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 4C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 4A and 4B in an overlappedstate;

FIG. 5A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 5B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 5C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 5A and 5B in an overlappedstate;

FIG. 6A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 6B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 6C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 6A and 6B in an overlappedstate;

FIG. 7A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 7B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 7C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 7A and 7B in an overlappedstate;

FIG. 8A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 8B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 8C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 8A and 8B in an overlappedstate;

FIG. 9A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 9B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 9C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 9A and 9B in an overlappedstate;

FIG. 10A is a schematic view of an opening pattern of a pixel electrodeaccording to the other example of the present invention;

FIG. 10B is a schematic view of an opening pattern of a common electrodeaccording to the other example of the present invention;

FIG. 10C is a schematic view of the opening patterns of the pixel andcommon electrodes shown respectively in FIGS. 10A and 10B in anoverlapped state;

FIG. 11 are schematic views of various types of opening patterns fordemonstrating the affect of opening pattern width and spacing onresponse speed and brightness;

FIG. 12A is a graph illustrating light transmissivity levels of testcells applying the opening patterns shown in FIG. 11;

FIG. 12B is a graph comparing the light transmissivity level of a testcell applying a specific opening pattern shown in FIG. 11 to the lighttransmissivity levels of test cells applying the other opening patternsshown in FIG. 11;

FIG. 13 is a graph illustrating response times as a function of grayscale of test cells applying the opening patterns shown in FIG. 11;

FIG. 14 is a graph illustrating response times as a function of grayscale of actual panels applying specific opening patterns shown in FIG.11;

FIGS. 15A to 15C are photographs of specific opening patterns shown inFIG. 11 at white gray scales;

FIGS. 16A and 16B are photographs of specific opening patterns shown inFIG. 11 used to illustrate a change in partitioned regions according toa level of an applied voltage;

FIGS. 17A and 17B are schematic views used to illustrate the change inintensity of a fringe field according to variations in opening patternwidth;

FIGS. 18A to 18D are schematic views illustrating orientation states ofliquid crystal molecules at a peripheral portion of opening patterns;

FIGS. 19 and 20 are schematic views of areas where texture occurs inspecific opening patterns shown in FIG. 11;

FIGS. 21A to 21C are schematic views of opening patterns where textureeliminating techniques have been applied.

FIG. 22 is a layout view of a TFT substrate according to the otherexample of the present invention.

FIG. 23 is a layout view of a color filter substrate opposite the TFTsubstrate in FIG. 22 according to the other example of the presentinvention.

FIG. 24 is a layout view of an LCD having the TFT substrate and thecolor filter substrate shown in FIGS. 22 and 23 according to the otherexample of the present invention.

FIG. 25 is a sectional view of the LCD shown in FIG. 24 taken along theline XXV-XXV′.

FIG. 26 is a layout view of a color filter substrate according to theother example of the present invention.

FIGS. 27 and 28 are layout views of LCDs according to the other exampleof the present invention respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be explained with referenceto the accompanying drawings.

FIG. 2 is a schematic cross sectional view of a liquid crystal displayaccording to a preferred embodiment of the present invention.

As shown in FIG. 2, the liquid crystal display includes lower and uppersubstrates 10 and 20 arranged substantially in parallel with apredetermined gap therebetween. Liquid crystal material is injectedbetween the lower and upper substrates 10 and 20 to form a liquidcrystal layer. The liquid crystal material is comprised of liquidcrystal molecules 30. A long axis of liquid crystal molecules 30 isoriented normal to the lower and upper substrates 10 and 20. Both thelower and upper substrates 10 and 20 are transparent material such asglass.

The lower substrate 10 is overlaid with a pixel electrode 12 that isconnected to a switching element 11 to receive display signals. Thepixel electrode 12 is formed of a transparent material such as indiumtin oxide (ITO) or indium zinc oxide (IZO), and has an opening pattern(not shown). The switching element 11 is, for example, a thin filmtransistor, and is connected to a gate line (not shown), which transmitsscanning signals, and a data line (not shown), which transmits picturesignals. The switching element 11 turns the pixel electrode 12 on andoff. A lower polarizer film 14 is attached to an outer surface of thelower substrate 10. In a reflection-type LCD, the pixel electrode 12 isformed of non-transparent material. In this case, the lower polarizerfilm 14 is not necessary.

All inner surface of the upper substrate 20 is sequentially overlaidwith a black matrix 21 that prevents the light leakage, a color filter22, and a common electrode 23. The common electrode 23 is formed of atransparent material such as ITO or IZO, and has an opening pattern (notshown). A polarizer film 24 is attached to an outer surface of the uppersubstrate 20. Alternatively, the black matrix 21 or the color filter 22may be formed on the lower substrate 10.

The LCD can be structured to operate in a normally black mode byarranging the lower polarizer film 14 and the upper polarizer film 24 sothat the polarizing directions of each film are perpendicular to eachother. It can also be structured to operate in a normally white mode byarranging the polarizing directions of each film to be parallel witheach other. In the following description, only the arrangement for anormally black mode will be described. However, the invention can bealso applied to the normally white mode. FIG. 3A shows a schematic viewof opening patterns of the pixel and common electrodes 12 and 23according to one example of the present invention. As shown in FIG. 3A,an opening pattern 101 of the pixel electrode 12 and an opening pattern102 of the common electrode are respectively formed in a straight line.The opening pattern 101 is substantially parallel to the opening pattern102. With this structure, the liquid crystal molecules 30 are arrangedin parallel as a result of a fringe field generated by the openingpatterns 101 and 102. Furthermore, the liquid crystal molecules 30 moveinto the parallel arrangement in a single step, thereby enabling a rapidresponse speed.

However, the above structure develops texture over a wide area of thescreen. It is also possible that white after-images appear on thescreen. When a screen displays a dark color on a bright background andthen returns to the color of the bright background, it becomes brightermomentarily than the bright background. It is called as “whiteafter-image”. FIG. 3B shows a schematic view of opening patterns of thepixel and common electrodes 12 and 23 according to another example ofthe present invention.

As shown in FIG. 3B, an opening pattern 111 of pixel electrode 12 and anopening pattern 112 of common electrode 23 are respectively formed in acurved shape. The ends of the opening patterns 111 and 112 arepositioned in close proximity and their centers are bulging in oppositedirections. However, this structure cannot arrange the liquid crystalmolecules 30 in a single step, resulting in a slow response speed.

In the following examples, opening patterns of the pixel and commonelectrodes 12 and 23 will be described with reference to one pixel area.In a single pixel area, the pixel electrode 12 is substantiallyrectangular in shape having first and second long sides, respectivelycorresponding to left and right sides (in the drawings) of the pixelelectrode 12. It has first and second short sides, respectivelycorresponding to top and bottom sides (in the drawings) of the pixelelectrode 12. It also has a first corner formed by the ends of the firstlong side and the first short side, a second corner formed by the endsof the first short side and the second long side, a third corner formedby the ends of the second long side and the second short side, and afourth corner formed by the ends of the first long side and the secondshort side. Further, the pixel electrode 12 includes an upper region anda lower region, the upper region corresponding to an upper half (in thedrawings) of the pixel electrode 12 and defined by the first long side,the second long side and the first short side, and the lower regioncorresponding to a lower half (in the drawings) of the pixel electrode12 and defined by the first long side, the second long side and thesecond short side.

As the common electrode 23 is present over the entire surface of theupper substrate 20, a portion of the common electrode 23 roughlycorresponding to the pixel electrode 12 in one pixel area will bedescribed. Here, such portions of the common electrode 23 will beindicated by a dotted line and the identifying markers (i.e., upperregion and lower region; first long side and second long side; firstshort side and second short side; and first, second, third and fourthcorners) used for ease of explanation of the pixel electrode 12, whichwill also denote these portions of the common electrode 23 defined bythe dotted lines.

FIG. 4A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention.

As shown in FIG. 4A, a middle opening 121 is formed inwardly from thefirst long side where the upper and lower regions of the pixel electrode12 meet. The middle opening 121 extends a predetermined distance towardthe second long side while being tapered. The first long side is cut ata predetermined angle on both sides of the middle opening 121, forming awide inlet area of the middle opening 121. Upper and lower openings 122and 123 are formed in the upper and lower regions of the pixel electrode12, respectively, proceeding from the second long side at apredetermined angle respectively toward the first and fourth corners ofthe pixel electrode 12 in a symmetrical manner.

FIG. 4B shows a schematic view of an opening pattern of the commonelectrode 23 according to the other example of the present invention.

As shown in FIG. 4B, the opening pattern of the common electrode 23includes middle, upper and lower openings 210, 220 and 230 respectivelyspaced apart from the other at predetermined distances. The middleopening 210 includes a trunk 211 positioned where the upper and lowerregions of the common electrode 23 meet and proceeding from the secondlong side a predetermined distance toward the first long side. First andsecond branches 212 and 214 are extended at a predetermined angle fromthe trunk 211 toward the first long side, and first and secondsub-branches 213 and 215 extend along the first long side respectivelyfrom the first and second branches 212 and 214, toward the first andsecond short sides, respectively. The upper opening 220, which is formedin the upper region of the common electrode 23, includes a first body221 that is formed extended from the second long side to the first shortside at a predetermined distance from the second corner and parallel tothe first branch 212. A first upper limb 222 extends from an end of thefirst body 221 along the first short side and until reaching the firstlong side, and a first lower limb 223 extends from an opposite end ofthe first body 221 along the second long side toward the second shortside. The lower opening 230 includes a second body 231, a second lowerlimb 232, and a second upper limb 233. The lower opening 230 is arrangedin the lower region and is symmetrical to the upper opening 220.

FIG. 4C shows a schematic view of the opening patterns of the pixel andcommon electrodes 12 and 23 shown respectively in FIGS. 4A and 4B in anoverlapped state.

As shown in FIG. 4C, the opening patterns of the pixel and commonelectrodes 12 and 23 divide the pixel electrode 12 into several regions.The openings 121, 122 and 123 of the pixel electrode 12 and the openings210, 220 and 230 of the common electrode 23 are alternately arrangedexcept where the trunk 211 of the middle opening 210 of the commonelectrode partially overlaps the middle opening 121 of the pixelelectrode 12.

In this preferred embodiment, the lower and upper polarizer films 14 and24 are arranged such that their polarizing directions are respectively0° and 90° (or vice versa) with respect to the first and second shortsides of the pixel electrode 12. With such an arrangement, when theliquid crystal molecules 30 are rearranged under the application of anelectric field, they cannot be oriented in the polarizing direction ofthe polarizer films 14 and 24, without causing the texture problems.Furthermore, as the liquid crystal molecules 30 are fully oriented inparallel under the influence of the fringe field, the movement of theliquid crystal molecules 30 is completed in one step, resulting in arapid response speed.

In addition, the opening portions of the pixel and common electrodes 12and 23 are arranged generally in two directions normal to each other.Since the opening portions of the pixel and common electrodes 12 and 23are alternately arranged, the fringe field is applied in four directionsat one pixel area. Therefore, wide viewing angles can be obtained in alldirections.

FIG. 5A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention. Asshown in FIG. 5A, the opening pattern of the pixel electrode 12 is aV-shaped opening 130. The V-shaped opening 130 has a vertex in proximityto the second long side and positioned where the upper region meets thelower region of the pixel electrode 12, and opens toward the first longside of the pixel electrode 12. That is, an upper half 131 of theopening 130 extends at a predetermined angle from the vertex of theopening 130 toward the first long side of the pixel electrode 12 suchthat the upper half 131 is positioned wholly in the upper region of thepixel electrode 12, and a lower half 132 of the opening 130 extends at apredetermined angle from the vertex of the opening 130 toward the firstlong side of the pixel electrode 12 such that the lower half 132 ispositioned wholly in the lower region of the pixel electrode 12.Further, the second and third corners of the pixel electrode 12 are cutaway to form a curved shape.

FIG. 5B shows a schematic view of an opening pattern of the commonelectrode 23 according to the other example of the present invention.

As shown in FIG. 5B, the opening pattern of the common electrode 23includes a right opening 240 and a left opening 250. The right opening240 includes a base 241 formed along and extending past the first longside of the common electrode 23, and tapers from a middle portion alongthe first long side toward the first and second short sides. The base241 of the right opening 240 also includes a projection 242 extending apredetermined distance from the base 241 toward the second long side andtapered in the same direction. A portion of the projection 242 adjacentto the base 241 is formed at a predetermined slant. The left opening 250includes a body 251 formed along the second long side of the commonelectrode 23, an upper limb 252 extended at a predetermined angle fromone end of the body 251 toward and continuing past the first corner ofthe common electrode 23, and a lower limb 253 extended at apredetermined angle from the other end of the body 251 toward andcontinuing past the fourth corner of the common electrode 23. Centers ofboth the right and left openings 240 and 250 are positioned where theupper and lower regions of the common electrode 23 meet.

FIG. 5C shows a schematic view of the opening patterns of the pixel andcommon electrodes 12 and 23 shown respectively in FIGS. 5A and 5B in anoverlapped state.

As shown in FIG. 5C, the opening patterns of the pixel and commonelectrodes 12 and 23 divide the pixel electrode 12 into several regions.The V-shaped opening 130 of the pixel electrode 12 is placed between theright and left openings 240 and 250 of the common electrode 23. Theupper and lower parts 131 and 132 of the V-shaped opening 130 proceed inparallel to the lower and upper limbs 252 and 253 of the left opening250, respectively, as well as to the portion of the projection 242adjacent to the base 241 of the right opening portion 240. An end of theprojection 242 overlaps the vertex of the V-shaped opening portion 130.With the configuration of this example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are the same as theprevious example.

FIG. 6A shows a schematic view of an opening pattern of the pixelelectrode 12 according to a fifth preferred embodiment of the presentinvention. As shown in FIG. 6A, the opening pattern of the pixelelectrode 12 includes an upper opening 141 formed in the upper region ofthe pixel electrode 12, and a lower opening 142 formed in the lowerregion of the pixel electrode. If the pixel electrode 12 is divided intothree areas of equal length, that is, first to third areas, with thefirst area having as its one side the first short side, the third areahaving as its one side the second short side, and the second area beingformed between the first and third areas, the upper opening 141 ispositioned where the first and second areas meet, and the lower opening142 is positioned where the second and third areas meet. The upperopening 141 extends from the first long side to the second long side ofthe pixel electrode 12 in the horizontal direction, and areas of thepixel electrode 12 corresponding to where the upper opening 141 ispositioned along the first long side are cut away to form a curvedshape. Similarly, the lower opening 142 extends from the second longside to the first long side of the pixel electrode 12 in the horizontaldirection. Areas of the pixel electrode 12 corresponding to where thelower opening 142 is positioned along the second long side are cut awayto form a curved shape. In addition, second and third corners of thepixel electrode 12 are cut such that they are rounded.

FIG. 6B shows a schematic view of an opening pattern of the commonelectrode 23 according to a fifth preferred embodiment of the presentinvention.

As shown in FIG. 6B, the opening pattern of the common electrode 23 is azigzag-shaped opening 260. The zigzag-shaped opening 260 includes anupper part 261 proceeding from the first corner of the common electrode23 at a predetermined slant toward and meeting the second long side ofthe common electrode 23. A middle part 262 extends at a predeterminedslant from an end of the upper part 261 where the same meets the secondlong side toward and meeting the first long side of the common electrode23. And a lower part 263 extends at a predetermined slant from an end ofthe middle part 262 where the same meets the first long side toward andmeeting the third corner of the common electrode 23. If the commonelectrode 23 is divided into three areas of equal length, that is, firstto third areas, with the first area having as its one side the firstshort side, the third area having as its one side the second short side,and the second area being formed between the first and third areas, theupper and middle parts 261 and 262 converge where the first and secondareas meet, and the middle and lower parts 262 and 263 converge wherethe second and third areas meet.

FIG. 6C shows a schematic view of the opening patterns of the pixel andcommon electrodes 12 and 23 shown respectively in FIGS. 6A and 6B in anoverlapped state.

As shown in FIG. 6C, the opening patterns of the pixel and commonelectrodes 12 and 23 divide the pixel electrode 12 into several regions.The portion where the upper and middle parts 261 and 262 of the opening260 of the common electrode 23 meet overlaps an end of the upper openingportion 141 of the pixel electrode 12 adjacent to the second long side,and the portion where the middle and lower parts 262 and 263 of theopening 260 of the common electrode 23 meet overlaps an end of the loweropening portion 142 of the pixel electrode 12 adjacent to the first longside.

With the configuration of the example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are the same as in theprevious examples.

FIG. 7A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention.

As shown in FIG. 7A, the opening pattern of the pixel electrode 12includes an upper opening 151 formed parallel to the first and secondshort sides in the upper region of the pixel electrode 12, and a loweropening 152 also formed parallel to the first and second short sides inthe lower region of the pixel electrode 12. If the pixel electrode 12 isdivided into three areas of equal length, that is, first to third areas,with the first area having as its one side the first short side, thethird area having as its one side the second short side, and the secondarea being formed between the first and third areas, the upper opening151 is positioned where the first and second areas meet, and the loweropening portion 152 positioned where the second and third areas meet.The upper and lower openings 151 and 152 extend from a position inproximity to the first long side to a position in proximity to thesecond long side.

FIG. 7B shows a schematic view of an opening pattern of the commonelectrode 23 according to a sixth preferred embodiment of the presentinvention.

As shown in FIG. 7B, the opening pattern of the common electrode 23includes first, second and third X-shaped openings 270, 280 and 290spaced apart from each other at a predetermined distance along thelength of the common electrode 23. A center area of each of the X-shapedopenings 270, 280 or 290 is cut away to form an enlarged areaapproximately rectangular in shape. One line forming the “X” of thefirst X-shaped opening 270 extends from the first corner to the secondlong side of the common electrode 23 and its other line extends from thesecond corner to the first long side of the common electrode 23.Likewise, one line forming the “X” of the second X-shaped opening 280extends from the first long side to the second long side of the commonelectrode 23 and its other line extends from the second long side to thefirst long side of the common electrode 23. In the same manner, one lineforming the “X” of the third X-shaped opening 290 extends from thesecond long side to the fourth corner of the common electrode 23 and itsother line extends from the first long side to the third corner of thecommon electrode 23.

FIG. 7C shows a schematic view of the opening patterns of the pixel andcommon electrodes 12 and 23 shown respectively in FIGS. 7A and 7B in anoverlapped state.

As shown in FIG. 7C, the opening patterns of the pixel and commonelectrodes 12 and 23 are alternately arranged, and divide the pixelelectrode 12 into several regions.

With the configuration of this example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are respectively 45° and135° (or vice versa) with respect to the first and second short sides ofthe pixel electrode 12.

FIG. 8A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention.

As shown in FIG. 8A, the opening pattern of the pixel electrode 12includes an upper opening 160 formed in the upper region of the pixelelectrode 12, and a lower opening 170 formed in the lower region of thepixel electrode 12. The upper opening 160 is T-shaped. That is, theupper opening 160 has a base 161 (the top of the “T”) formed at apredetermined distance from where the upper and lower regions of thepixel electrode 12 meet. The base 161 extending from approximately thefirst long side to the second long side of the pixel electrode 12. Theupper opening 160 also has a protrusion 162 extending substantially froma center of the base 161 in a direction toward the first short side ofthe pixel electrode 12, thereby bisecting the upper region of the pixelelectrode 12 into left and right sub-areas. The lower opening 170 isformed parallel to the base 161 of the upper opening 160 and extendsacross the pixel electrode 12 approximately and at predetermineddistances from the first long side to the second long side of the pixelelectrode 12 such that the lower opening 170 bisects the lower region ofthe pixel electrode 12 into upper and lower sub-areas.

FIG. 8B shows a schematic view of an opening pattern of the commonelectrode 23 according to the other example of the present invention.

As shown in FIG. 8B, the opening pattern of the common electrode 23includes two upper openings 310 and 320, a middle opening 330, and alower opening 340. The two upper openings 310 and 320 are spaced apartfrom each other at a predetermined distance in the upper region of thecommon electrode 23, and are parallel to each other as well as to thefirst and second long sides of the common electrode 23. The middle andlower openings 330 and 340 are spaced apart from each other at apredetermined distance in the lower region of the common electrode 23,and are parallel to each other and to the first and second short sidesof the common electrode 23. Both end portions of the middle and loweropenings 330 and 340 are enlarged in roughly a triangular shape, and thetriangle-shaped end portions of the middle and lower opening portions330 and 340 proceed over the first and second long sides of the commonelectrode 23.

FIG. 8C shows a schematic view of the opening patterns of the pixel andcommon electrodes 12 and 23 shown respectively in FIGS. 8A and 8B in anoverlapped state.

As shown in FIG. 8C, the opening patterns of the pixel and commonelectrodes 12 and 23 divide the pixel electrode 12 into several regions.That is, ends of the upper opening portions 310 and 320 of the commonelectrode 23 farthest from the first short side of the common electrode23 overlap the base 161 of the T-shaped opening 160 of the pixelelectrode 12. Accordingly, the upper openings 310 and 320 of the commonelectrode 23, and the protrusion 162 of the T-shaped opening 160 of thepixel electrode 12 divide an area of the pixel electrode 12 defined bythe base 161 of the T-shaped opening 160, the first and second longsides of the pixel electrode 12, and the first short side of the pixelelectrode 12 into four sub-areas. The middle and lower openings 330 and340 of the common electrode 23, and the lower opening 170 of the pixelelectrode 12 divide an area of the pixel electrode 12 defined by thebase 161 of the T-shaped opening 160, the first and second long sides ofthe pixel electrode 12, and the second short side of the pixel electrode12 into four sub-areas.

With the configuration of this example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are the same as in theimmediate previous example. Accordingly, the orienting direction, of theliquid crystal molecules 30 becomes 45° with respect to the polarizingdirection of the polarizer films 14 and 24 so that the response speed israpid and the texture is decreased, resulting in enhanced picturequality. The opening portions of the pixel and common electrodes 12 and23 proceed generally in two directions normal to each other.Furthermore, as the opening portions of the pixel and common electrodes12 and 23 are alternately arranged, the fringe field in one pixel areais applied in all directions.

FIG. 9A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention. Asshown in FIG. 9A, the opening pattern of the pixel electrode 12 is asingle linear opening 180 parallel to the first and second short sidesof the pixel electrode 12. If the pixel electrode 12 is divided intothree areas of equal length, that is, first to third areas, with thefirst area having as its one side the first short side, the third areahaving as its one side the second short side, and the second area beingformed between the first and third areas, the linear opening 180 ispositioned where the second and third areas meet.

FIG. 9B shows a schematic view of an opening pattern of the commonelectrode 23 according to the other example of the present invention.

As shown in FIG. 9B, the opening pattern of the common electrode 23includes an upper opening 350 formed in the upper region of the commonelectrode 23 and a lower opening 360 formed in the lower region of thecommon electrode. The upper opening 350 includes a base 351, a trunk352, and two branches 353 and 354. The base 351 of the upper opening 350is formed roughly in a triangular shape and positioned extending overand past the first short side of the common electrode 23. The trunk 352is linearly extended from an apex of the base 351 in a direction towardthe second short side of the common electrode 23. The branches 353 and354 are branched from a distal end of the trunk 352 toward and extendingover the first and second long sides of the common electrode 23, each ofthe branches 353 and 354 forming an obtuse angle with respect to thetrunk 352. The lower opening 360 linearly proceeds in a directionparallel to the first and short sides of the common electrode 23. Bothends of the lower opening 360 are enlarged in roughly a triangular shapeand extend over the first and second long sides of the common electrode23.

FIG. 9C shows a schematic view of the pixel and common electrodes 12 and23 shown respectively in FIGS. 9A and 9B in an overlapped state.

As shown in FIG. 9C, the branches 353 and 354 of the upper opening 350of the common electrode 23 roughly divide the pixel electrode 12 intoupper and lower areas. The trunk 352 of the upper opening 350 of thecommon electrode 23 bisects the upper area of the pixel electrode 12into two sub-areas, one sub-area having as its one side the second longside of the pixel electrode 12 and the other sub-area having as its oneside the first long side of the pixel electrode 12. The lower opening360 of the common electrode 23, and the linear opening 180 of the pixelelectrode 12 trisect the lower area of the pixel electrode 12 intoupper, middle and lower sub-areas.

With the configuration of this example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are the same as in theimmediate previous example. With this structure, effects similar tothose obtained in the previous example are realized.

FIG. 10A shows a schematic view of an opening pattern of the pixelelectrode 12 according to the other example of the present invention.

As shown in FIG. 10A, the pixel electrode 12 is formed of fouroval-shaped portions sequentially interconnected in the longitudinaldirection.

FIG. 10B shows a schematic view of an opening pattern of the commonelectrode 23 according to the other example of the present invention.

As shown in FIG. 10B, the opening pattern of the common electrode 23includes four diamond-shaped openings 370, and left and right openings380 and 390 surrounding the diamond-shaped openings 370. Thediamond-shaped openings 370 are arranged over a longitudinal center ofthe common electrode 23 and are spaced apart from each other at apredetermined distance. Inner sides of the left and right openings 380and 390 facing the diamond-shaped openings 370 substantially formcycloids such that four partial ovals result, each oval surrounding oneof the diamond-shaped openings 370.

FIG. 10C shows a schematic view of the pixel electrode 12 and the commonelectrode 23 shown respectively in FIGS. 10A and 10B in an overlappedstate. As shown in FIG. 10C, each diamond-shaped opening 370 of thecommon electrode 23 is placed at the center of the correspondingoval-shaped portion of the pixel electrode 12. Also, the left and rightopenings 380 and 390 of the common electrode 23 surround the pixelelectrode 12 at a predetermined distance.

With the configuration of this example of the present invention asdescribed above, the lower and upper polarizer films 14 and 24 arearranged such that their polarizing directions are respectively 0° and90° (or vice versa) with respect to the first and second short sides ofthe pixel electrode 12. The opening patterns of the pixel and commonelectrodes 12 and 23 in these example were designed to satisfy thefollowing conditions to the most, the conditions being particular toopening patterns of the type for obtaining the partitioned orientationof the liquid crystal molecules 30.

First, in order to obtain a maximum viewing angle, it is preferable thatone pixel area has four partitioned regions for orienting the liquidcrystal molecules 30.

Second, to obtain a stable partitioned orientation, disinclination ortexture should be eliminated or minimized outside of the partitionedregions. Disinclination occurs when the long axes of liquid crystalmolecules are oriented in various directions in a confined area,particularly when the long axes are inclined toward one another.Therefore, it is preferable that the opening patterns of the pixel andcommon electrodes 12 and 23 are alternately arranged, and the endportions of the opening patterns are adjacent to each other. That is,when viewed from above, the opening patterns of the pixel and commonelectrodes 12 and 23 are preferably structured in the form of closedpolygons. Furthermore, since disinclination is prone to occur when theopening patterns are structured having acute angles, it is preferablethat the opening patterns are formed to have only obtuse angles. Astable partitioned orientation of liquid crystal molecules also enhancesbrightness. At areas where the orientation of the liquid crystalmolecules 30 is dispersed, lights tend to leak at an off state, and darkportions are generated at an on state. Also, this dispersion of theorientation of liquid crystal molecules generates after-images when theliquid crystal molecules are rearranged.

Third, in order to obtain a high level of brightness, the followingconditions should be satisfied. The angle made by the two directors ofthe liquid crystal molecules 30 at adjacent partitioned regions ispreferably about 90°. The directors arranged at this angle minimizes thedisinclination. The best brightness can be obtained when the anglebetween the light transmission axis of the polarizer film and thedirector for liquid crystal molecules is 45°. It is preferable thattwisting or bending of the opening patterns of the pixel and commonelectrodes 12 and 23 is minimized.

Finally, in order to obtain a rapid response speed of the liquid crystalmolecules 30, it is preferable again that the opening patterns of thepixel and common electrodes 12 and 23 are neither twisted nor bent toomuch. That is, it is preferable that the opening patterns of the pixeland common electrodes 12 and 23 linearly face each other.

The effect of an opening width of the opening patterns and a spacinginterval between the openings on light transmission and response speedwill now be described.

In order to investigate such an interrelation, nine panels, each withdifferent opening patterns were made and tested.

FIG. 11 shows schematic views of nine different opening patterns A-J fordemonstrating the effect of opening pattern width and spacing onresponse speed and brightness. In the drawing, the opening patterns ofthe common electrode are indicated by hatched lines, and the openingpatterns of the pixel electrode are indicated by solid lines.

As shown in FIG. 11, the B, C and D opening patterns are identical andthe B, F and G opening patterns are identical. However, these openingpatterns differ in opening width and spacing. The I and J openingpatterns differ in the number of openings used, effectively havingdifferent opening spacings. The A opening pattern has a shape similar tothat of the B, C and D opening patterns except for the formation at acenter area of the A opening pattern. As a result, the A opening patternis different in opening spacing from the B, C and D opening patterns.The opening width and the opening spacing of each opening pattern arelisted in Table 1.

TABLE 1 Opening Width (μm) Opening Spacing (μm) A 10 33.5 B 10 22.5 C 725.5 D 13 19.6 E 24 F 21 G 27 I 10 Narrow Spacing: 29 Wide Spacing: 32 J10 Narrow Spacing: 10 Wide Spacing: 16

FIG. 12A is a graph illustrating light transmissivity levels of testcells applying the A through J opening patterns, and FIG. 12B is a graphcomparing the light transmissivity level of a test cell applying the Bopening pattern to the light transmissivity levels of test cellsapplying the A through J opening patterns. As shown in the graphs, thelight transmissivity level of the test cell applying the G openingpattern is the highest, exceeding 13%. The ranking of the lighttransmissivity levels of the test cells from highest to lowest accordingto which opening pattern is used is G, E, I, B, D, A, C, F, and J inorder.

FIG. 13 is a graph illustrating response times as a function of grayscale of test cells applying the A through J opening patterns. Althoughonly sixty-nine (69) gray scales are used in an actual application, theexperiment was performed with one hundred and ten (110) gray scales. Asshown in the graph, response times of the test cells applying the B, C,D, and J opening patterns were relatively fast over the whole range ofgray scales. For the test cells applying the other opening patterns, theresponse times were relatively slow. In the case of the test cellsapplying the A and I opening patterns, the slow response times were dueto the movement of texture. In the case of the test cells applying theE, F, and G opening patterns, the slow response times can be attributedto the two-step movement of liquid crystal molecules.

The A through J opening patterns shown in FIG. 11 were applied to actualpanels and the panels were tested. Testing was performed on a total offour panels for each opening pattern. The results are listed in Table 2.

TABLE 2 White White T Ton Toff Ttotal after- T Ton Toff Ttotal after-PTN (%) (ms) (ms) (ms) image (%) (ms) (ms) (ms) image A 5.50 21.53 20.3841.73 Medium 5.12 18.56 13.99 32.55 Weak 5.44 19.14 20.18 39.32 Strong4.27 14.69 15.15 29.84 Weak B 5.23 18.16 20.28 38.44 very weak 4.7912.36 14.5 26.86 X 4.88 18.79 20.42 39.21 very weak 4.56 12.64 15.4828.12 X C 4.96 18.8 21.6 40.4 Strong 4.07 9.6 14.8 24.4 Strong 4.19 8.9814.3 23.28 Strong D 4.88 24.36 21.2 40.0 X 4.75 12.8 14.8 27.6 X 4.7913.36 13.47 26.83 X E 5.52 22.2 21.69 46.05 very weak 5.34 44.11 14.2858.39 X 5.58 23.67 20.0 42.2 very weak F 4.79 20.8 21.63 45.2 X 4.3470.79 14.89 85.68 X 5.58 20.8 19.2 40.0 X I 5.51 15.0 21.6 42.4 Weak4.99 10.4 13.0 23.4 very weak 4.77 12.6 15.4 28 X J 4.76 20.8 35.8 Weak4.49 7.6 12.4 20.0 Weak 3.96 9.6 15.4 25.0 Weak

The results of the experiment performed with the actual panels weresimilar to the results when using the test cells. However, there weresome differences as follows. First, the actual panel of the I openingpattern exhibited a higher response speed than the test cell of the sameopening pattern. Also, better results with regard to brightness wereobtained with the actual panel of the J opening pattern than when thetest cell was used. Specifically, the brightness of the test cellapplying the J opening pattern was 75% of the cell applying the Bopening pattern, whereas this was increased to 90% when the J openingpattern was applied to the actual panel.

When the actual panels were used, white after-images were generated withthe application of the C, I, and J opening patterns. The whiteafter-image appeared too much with the application of the C openingpattern that picture quality was impaired beyond the tolerance. However,the generation of white after-images was low enough when the I and Jopening patterns were applied so that with some improvement, the panelscould be used.

On the basis of the above results, the opening patterns are to beselected depending on what the intended area of improvement is. If theimprovement of brightness and the minimization of white afterimages aredesired, it is preferable to use the B, D, E, and I opening patterns.However, if an improvement in response speed while keeping thebrightness at a normal level is desired, the B, D, and I openingpatterns are preferred. Finally, if what is needed is solely animprovement in response speed (without concerning brightness), the D andJ opening patterns are preferred.

In order to further examine the interrelation between the response speedand the opening width of the opening patterns, the differences in theoptical characteristics of panels applying the B, C, and D openingpatterns, which have the same shape but different opening widths, willnow be described. FIG. 14 is a graph illustrating response times as afunction of gray scale of actual panels applying the B, C, and D openingpatterns. As shown in the graph, the response times of the panelsapplying the opening patterns exhibited the following relation (based onthe type of opening pattern) when 20 to 40 gray scales were used: D<B<C.It is evident, therefore, that the larger the width of the openingpattern the faster the response time.

Roughly between 40 and 45 gray scales, the response time of the panelapplying the C opening pattern is shorter than that of the panelapplying B opening pattern, and after 45 gray scales, the response timeof the panel applying the C opening pattern is shorter than that of thepanel applying the D opening pattern. However, such a change in theresponse time of the panel applying the C opening pattern is notactually taking place, but instead is given the appearance of change asa result of the generation of white after-images. That is, the responsewaveform is distorted due to the white after-images so that the responsetime seems to be shorter than it actually is. Accordingly, theconclusion originally reached that the larger the width of the openingpattern the faster the response speed remains valid.

With the use 60 gray scales or more, the response speed slowsconsiderably due to the occurrence of texture. In conclusion, the panelapplying the D opening pattern, which has the greatest width, exhibitsthe most stable characteristics. FIGS. 15A to 15C are photographs of theC, B and D opening patterns, respectively, at white gray scales. As seenfrom the photographs, the C opening pattern with poor texture stabilitydisplays the lowest level of brightness, with the B and D openingpatterns exhibiting similarly higher levels of brightness. The D openingpattern exhibits a low opening ratio due to its significant width, butdisplays good texture stability such that panels applying this openingpattern have a high brightness. Texture stability is determined by theintensity of the fringe field and the width of the opening pattern.

The boundary areas between adjacent partitioned regions in the C, B andD opening patterns are formed differently. That is, two clearlydistinguishable textures are present in most of the boundary areas ofthe C opening pattern, and with the B opening pattern, the boundaryareas are again distinguishable but not as clearly as with the C openingpattern. The boundary areas of the D opening pattern, on the other hand,are not clearly formed and are faint in many portions.

FIGS. 16A and 16B are photographs of the C and D opening patternsapplied to test cells in which a change in the partitioned regionsaccording to a level of an applied voltage is shown.

In the C opening pattern, two clearly distinguishable textures arepresent in the boundary areas when the applied voltage reaches 3.5V, andbecomes clearer with further increases in the applied voltage. However,in the D opening pattern, the boundary areas are somewhat clearlydistinguishable only when the applied voltage reaches 5V. Suchdistinguishable boundary areas are a result of the non-uniformorientation of the liquid crystal molecules. To better describe such aphenomenon, the intensity of the fringe field as a function of thewidths of the opening patterns will be examined.

FIGS. 17A and 17B are schematic views used to illustrate the changes inthe intensity of a fringe field according to variations in openingpattern width. As the width of the opening pattern becomes larger, thehorizontal component of the fringe field experiences correspondingincreases. The horizontal component of the fringe field plays animportant role in determining the orienting direction of liquid crystalmolecules. Therefore, opening patterns with a large width are preferredin forming partitioned regions. In contrast, the larger the width of theopening pattern the weaker the intensity of the vertical component ofthe electric field working at the center of the opening pattern.

FIGS. 18A to 18D are schematic views illustrating orienting states ofliquid crystal molecules at a peripheral portion of the openingpatterns. When the width of the opening pattern is relatively small, theliquid crystal molecules are horizontally oriented to some degree evenat the center area of the opening pattern. That is, they are slightlyinclined when the applied voltage is low, but completely oriented in thehorizontal direction when the applied voltage is high. This is due tothe vertical component of the electric field being strong even at thecenter area of the opening pattern. As a result, the light tends to leakand the boundary area between the partitioned regions is formed by twoseparate lines. Furthermore, when the orienting direction of the liquidcrystal molecules is changed by 180°, elasticity becomes greater due tothe small width of the opening pattern. In contrast, as the horizontalcomponent of the fringe field is weak, the fringe field is not strongenough to overcome the elasticity, thereby resulting in the orientingdirection of the liquid crystal molecules at the boundary areas becomingnon-uniform between the partitioned regions. Such a non-uniformorientation of the liquid crystal molecules occurs even in micro regionsof the pixel.

When the width of the opening pattern is relatively large, the long axesof the liquid crystal molecules are perpendicular to the electrodes atthe center area of the opening pattern. As the applied voltage isincreased, the liquid crystal molecules are slightly inclined, but thedegree of inclination is less than when the opening pattern has a smallwidth. Therefore, only a minimal amount of light leaks and the boundaryarea between adjacent partitioned regions is shaped with a dark line.

As described previously, the greater the width of the opening patternthe more rapid the response speed, and as stated above, a greater widthof the opening pattern leads to more uniform micro regions of the pixel.When the width of the opening pattern is great, although the openingratio is low, the orientation of the liquid crystal molecules is uniformenough to obtain a satisfactory degree of brightness. According to theabove experimental results, it is preferable that the opening width ofthe opening pattern is in the range of 13±3 μm, and the cell gap is inthe range of about 4-6 μm.

The effect of opening spacing on the optical characteristics of theopening patterns will now be described.

The I and J opening patterns have the same total widths but effectivelydifferent spacings. According to the experimental results with respectto the test cells, the optical characteristics of the I and J openingpatterns are significantly different. However, when actual panels applythese opening patterns, the resulting optical characteristics of the Iand J opening patterns do not vary by such a degree. It is viewed thatthis is a result of the such factors as the difference in the type ofalignment layer used, whether a protective insulating layer is used, thedifference in the waveforms of the applied voltage, etc. However, whenthe speeds of moving picture images are compared in the actual panels,they are more rapid with the J opening pattern than with the I openingpattern. This can be easily demonstrated by observing the motion of adark rectangle on a gray background. The only difference in responsespeed occurs by variations in the gray scales.

Regarding the opening width of the opening pattern, when the spacingbetween the opening portions of the opening pattern becomes smaller, theopening ratio is significantly reduced but the brightness does notchange much. This is due to texture. That is, when the distance betweenthe opening portions is increased, it becomes difficult to control thetexture, whereas it can be easily controlled when the opening spacing issmall. Therefore, when the distance between the opening portions issmall, the opening ratio is reduced but it becomes easy to control thetexture which compensates the brightness. The exception is the I openingpattern, in which even though the distance between the opening portionsis large, a high brightness can be achieved because texture is easilycontrolled.

In brief, a smaller distance between the opening portions results in animprovement of the response speed at various gray scales. Even thoughthe brightness is negatively affected due to the decreasing openingratio, this can be compensated for to some degree by controllingtexture.

There exists a direct correlation between texture and response speed.Moving texture reduces response speed. When a high voltage is applied,the response speed is reduced in most of the opening patterns. This isdue to the generation of texture. Therefore, if texture can be properlycontrolled, picture quality as well as response speed can be improved.Techniques of preventing texture will now be described.

FIGS. 19 and 20 show schematic views of portions where texture isgenerated in the B and J opening patterns, respectively. The openingpattern shown in FIG. 19 is nearly identical to that shown in FIG. 4C.However, in the opening pattern of FIG. 19, second and third openings122 and 123 of the pixel electrode 12 begin from the first long side ofthe pixel electrode 12 and extend toward the second long side of thepixel electrode 12 nearly reaching the same, whereas in the openingpattern of FIG. 4C, the second and third openings 122 and 123 arestructured in the opposite manner. Furthermore, portions of the secondlong side of the pixel electrode 12 adjacent to ends of the second andthird openings 122 and 123 of the opening pattern of FIG. 19 areprotruded externally to prevent the interconnection of the partitionedregions of the pixel electrode 12 from deteriorating due to the openingportions 122 and 123.

Portions where texture occurs mainly correspond to areas where ends ofthe opening portions of the common electrode 23 and ends of the openingportions of the pixel electrode 12 meet. When the upper and lowersubstrates are appropriately arranged, the occurrence of texture is low,whereas when the substrates are inappropriately arranged, halfmoon-shaped textures, which do not cause the generation of whiteafter-images, occur. In order to inhibit such texture occurrence, thewidth of the ends of the opening portions of the common electrode 23 maybe enlarged. Through such enlargement, the tolerance of error inarrangement can be increased.

The opening pattern shown in FIG. 20 is similar to that shown in FIG.8C, but differs in the number of openings extending across the pixelelectrode from the first long side to the second long side. Furthermore,the openings of the pixel electrode 12 are such that they are open wherethey begin at the first long side of the pixel electrode 12 and extendacross toward, but not reaching, the second long side of the pixelelectrode 12. Portions of the second long side of the pixel electrode 12adjacent to ends of these openings are protruded externally.

The occurrence of texture is concentrated at areas “a” corresponding toends of openings of the common electrode 23 proceeding across from thefirst long side to the second long side of the common electrode 23.Furthermore, texture occurs also along the second short side of thepixel electrode 12, or area “b”, which is deformed outwardly to enable aconnection with the source electrode, as well as at area “c” at an endof an opening of the pixel electrode 12.

Such texture can be inhibited in the following way. In the case of areaa, a width of the ends of the openings of the common electrode 23 areincreased. In the case of area b, the openings of the common electrode23 are structured to overlap part of area b. For this purpose, it isnecessary to control the width and spacing of the opening portions. Whenthe spacing is decreased, the opening ratio is reduced but the responsespeed is enhanced. In the case of area c, the end of the opening of thepixel electrode 12 extended from the first short side is formed havingsharp edges.

FIGS. 21A to 21C illustrate opening patterns where the above-describedtexture eliminating techniques have been applied.

In the above description, a structure in which the opening patterns areformed at both the pixel and common electrodes 12 and 23 is disclosed.However, it is also possible to form the opening patterns, together withthe protrusions, only at the pixel electrode 12. In this case, theprotrusions are formed using a gate insulating layer or a protectivelayer. In the formation of the protrusions, care should be taken toavoid the formation of parasitic capacitance between electrical lines.The openings and the protrusions can be arranged as illustrated in FIG.21.

Alternatively, the opening patterns may be formed only in the pixelelectrode 12 while forming the protrusions in the common electrode 23.In this case, the openings and the protrusions can be arranged also asillustrated in FIG. 21.

As described above, the inventive liquid crystal display obtains a wideviewing angle, and exhibits stable orientation of the liquid crystalmolecules and a rapid response speed.

FIGS. 22 and 23 are layout views of a TFT substrate and a color filtersubstrate according to the other examples respectively.

As shown in FIG. 22, a portion 210 of a gate line 21 which transmits ascanning signal is formed to have a trapezoidal shape without the lowerside. Then, the portion 210 made of opaque metal blocks the light fromthe backlight, and, therefore the light leakage or the decrease ofluminance can be prevented.

Next, as shown in FIG. 23, a black matrix 11 is formed on the colorfilter substrate to cover the regions where disclination is generatedand the aperture in the common electrode. The disclination regions are,as described above, the region where the aperture 27 on the TFTsubstrate meets the boundary of the pixel electrode 20 and the regionwhere the saw-shaped apertures 17 and 27 are bent. The black matrixpattern which covers the disclination includes, as shown in FIG. 23, anedge portion 111 surrounding and defining a pixel region, a saw-shapedportion 112 to cover the apertures 17, a triangular portion 113 to coverthe disclination between saw-shaped apertures 17 and 27 and a centerportion 114 put across the pixel region to cover the disclinationgenerated in the bent portion of the apertures 17 and 27. Then, thelight leakage generated by the disclination or the apertures isprevented by the black matrix 11. Moreover, the aperture ratio does notdecrease additionally though a relatively large area of black matrix 11is formed, because the region that the black matrix covers may not beused for display.

FIG. 24 is a layout view of an LCD according to the other example of thepresent invention. FIG. 25 is a sectional view of an LCD shown in FIG.24 taken along the line XXV-XXV′.

As shown in FIGS. 24 and 25, a portion 210 of a gate line 21 is formedon a lower TFT substrate. The gate line has a trapezoidal shape withoutthe lower side. An insulating layer 22 covers the gate line 21. A pixelelectrode 23 is formed on the insulating layer 22, and portions of thepixel electrode 23 are removed to form saw-shaped apertures 27 over theportion 210 of the gate line 21. A vertical alignment layer 24 is formedon the pixel electrode 20.

On the other hand, a black matrix 11 is formed on an upper color filtersubstrate to shield the outside of the pixel regions, the aperture andthe disclination regions. In the pixel region the black matrix 11, acolor filter 12 is formed. A passivation layer 15 is formed on the blackmatrix 11 and the color filter 12. An ITO common electrode 13 is formedthereon and patterned to remove the portion overlapping the black matrix11. The aperture 17 formed on the upper substrate is arrangedalternately to the aperture 27 formed on the lower substrate, and theapertures 17 and 27 are parallel to each other.

A liquid crystal material layer with negative dielectric anisotropy isinterposed between two substrate 100 and 200, and the liquid crystalmolecules are homeotropically aligned to the substrates 100 and 200 bythe aligning force of the alignment layers 14 and 24.

It is possible to form a gate line as in a conventional LCD and theapertures formed on the lower substrate is also covered by the blackmatrix, as shown in FIG. 26 which is a layout view of a color filtersubstrate according to the other example of the present invention.

A black matrix 11 is formed to define a pixel region and to cover theaperture 17 to form multi-domain, the disclination between saw-shapedapertures 17 and 27 and the disclination generated in the bent portionof the apertures 17 and 27 as in the immediate previous example. Inaddition, the black matrix 11 includes another portion to cover theaperture 27 formed on the lower substrate.

If the black matrix covers the apertures and the disclination as in thisexample, it is not necessary to consider the influence by the gate linepattern and no additional process step is required.

Moreover, the shape of the pixel electrode may be changed instead offorming the branch aperture in some of the previous examples.

As shown in the above, the region where the disclination is generated isthe region where the aperture on the TFT substrate meets the boundary ofthe pixel electrode. This region is the place where the first conditionthat the bent angle of the aperture pattern should be an obtuse angle isnot satisfied because the boundary of the pixel electrode is essentiallysimilar to the aperture. In other words, the liquid crystal molecules donot arrange in order and such arrangement causes the decrease of theluminance and after-image.

Therefore, in the other example of the present invention, the shape ofthe pixel electrode 21 is changed to make an angle between the aperture27 formed in the pixel electrode 21 and the boundary of the pixelelectrode 21 to be an obtuse angle. Then, as shown in FIG. 27, the pixelelectrode 21 has a saw shape that is convex between the apertures 17 and27 formed in the common electrode and the pixel electrode respectively.

In the other example of the present invention as shown in FIG. 28, thepixel electrode is formed to have a saw shape surrounding the apertures.

Since the pixel electrode 22 is formed to have a saw shape surroundingthe apertures 17 and 27, the regions where the apertures 17 and 27 meetthe boundary of the pixel electrode are removed thereby removing thedisclination.

According to the embodiments of the present invention, multi-domain LCDsare formed using various ITO pattern to control the arrangement ofliquid crystal molecules, therefore wide viewing angle is obtained,disclination is removed and the luminance is increased.

In the described embodiments of the present invention, only aperturesform the domains. However, the domains may be formed by protrusionsalong with apertures. In this case, the protrusions may be made of agate insulating layer and/or a passivation layer. The layout of theprotrusions and the aperture pattern may be the same as that of theapertures in FIGS. 21A to 21C. The protrusions may be formed on thecolor filter substrate.

While the present invention has been described in detail with referenceto the preferred embodiments, those skilled in the art will appreciatethat various modifications and substitutions can be made thereto withoutdeparting from the spirit and scope of the present invention as setforth the appended claims.

1. A liquid crystal display, comprising: a first substrate on which afirst electrode is formed; a second substrate on which a secondelectrode is formed; and liquid crystal positioned between the first andsecond substrates, wherein: the first electrode includes a first domainforming member and the second electrode includes a second domain formingmember, the first domain forming member includes a first trunk portion,the second domain forming member includes a second trunk portion, firstand second branches extending from the second trunk portion, and firstand second sub-branches respectively extending from ends of the firstand second branches, the first and second trunk portions aresubstantially parallel to a first side of the first electrode, at leasta portion of the first trunk portion and a portion of the second trunkportion overlap each other, the first and second sub-branches overlap atleast one edge of the first electrode.
 2. The liquid crystal display ofclaim 1, wherein the first and second domain forming members includeprotrusions or opening patterns.
 3. The liquid crystal display of claim1, wherein the first and second domain forming members are formed in apixel area and are separated from domain forming members formed in anadjacent pixel area.
 4. The liquid crystal display of claim 1, whereinthe first and second sub-branches are oblique to the first and secondbranches and extend along a second side of the first electrodesubstantially perpendicular to the first side.
 5. The liquid crystaldisplay of claim 4, wherein the first domain forming member includesopening patterns and the second domain forming member includesprotrusions.
 6. The liquid crystal display of claim 1, wherein thesecond domain forming member further includes an upper body including afirst limb extending therefrom along the first side of the firstelectrode and oblique to the upper body.
 7. The liquid crystal displayof claim 6, wherein the upper body extends from the first side of thefirst electrode to a second side of the first electrode, wherein thefirst side is substantially perpendicular to the second side.
 8. Theliquid crystal display of claim 6, wherein the upper body extends fromthe first side of the first electrode to a second side of the firstelectrode, wherein the first side is shorter than the second side. 9.The liquid crystal display of claim 6, wherein the upper body furtherincludes a second limb extending therefrom along a second side of thefirst electrode and oblique to the upper body.
 10. The liquid crystaldisplay of claim 9, wherein the second domain fainting member furtherincludes a lower body including a third limb extending therefrom alongthe second side of the first electrode and oblique to the lower body.11. The liquid crystal display of claim 6, wherein the second domainforming member further includes a lower body including a second limbextending therefrom along a second side of the first electrode andoblique to the lower body.
 12. The liquid crystal display of claim 11,wherein the second side is opposite to the first side.
 13. The liquidcrystal display of claim 6, wherein the second domain forming memberfurther includes a lower body including a second limb extendingtherefrom substantially parallel to the first limb and oblique to thelower body.
 14. The liquid crystal display of claim 13, wherein theupper and lower bodies are formed in a pixel area and are separated fromdomain forming members of an adjacent pixel area.
 15. The liquid crystaldisplay of claim 9, wherein at least a portion of the first limb and aportion the second limb overlap at least one edge of the firstelectrode.